1. Field of the Invention
The present invention relates to the field of bearings, particularly high performance bearings for planar movement of low mass objects.
2. Statement of the Problem
It is often necessary to provide bearings between two surfaces undergoing relative movement to reduce friction and provide support and guidance between these surfaces. Typically, these bearings consist of ball or roller bearings. However, in high precision applications, problems associated with the use of ball or roller bearings may arise. For example, actuator mechanisms in high performance disk drive systems frequently use ball bearings to provide stiff, low friction, precision guidance for the actuator. Problems existing with this application of ball bearings include friction, high mass, low damping capability, wear, particulate contamination and alignment.
Although the friction of ball bearings is low, it is not negligible in high performance drives. This friction affects the performance characteristics of the drive. The mass of the ball bearings form a significant part of the moving mass in a high performance disk drive. The high mass and stiffness of the ball bearings also create a lack of damping in the ball bearings, thus increasing the susceptibility of the drive to vibration.
The ball bearings also form a highly stressed point contact with the rails or support structure, causing wear and particulate contamination at the point of rolling contact. This affects the accuracy of the drive. The bearing grease used to lubricate the balls tends to dry out as well, leaving a residue which causes detenting of the bearing.
Another problem with the use of ball bearings is that the ball bearings must be critically aligned, which is difficult to achieve as well as difficult to maintain. The ball bearings can produce non-repeatable offtrack of the Read/Write heads mounted on the actuators due to ball drop within the bearing and to outer race runout.
Thus, a need exists for a bearing having a low mass, low contact stress, low friction, as well as not requiring alignment or lubrication, and not susceptible to vibration and to wear or particulate contamination.